Block-inversion-coded QAM systems

A novel block inversion code (BIC) which is both simple and effective in controlling low-frequency components of multilevel data signals is introduced, and its power spectrum is analyzed. The BIC's effect on the performance of QAM modems is studied, and an expression for the coded modem's symbol error rate is obtained. The code allows M-ary QAM system designs to incorporate unmodulated carrier-pilot insertion techniques using high-pass filters, for more robust, unambiguous carrier recovery and automatic gain control. The effect of BIC coding on the performance of a 256 QAM modem with carrier-pilot insertion using high-pass filters is investigated. It is found that, under some circumstances, BIC coding can significantly reduce the ill-effect of the high-pass filter on the modem's performance.<
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